Conventionally, there is a lock mechanism of a tube coupling that has, for performing quick insert/mount, a configuration in which a tubular body (plug) is inserted in a lock mechanism main body (socket), to automatically rotate a sleeve rotatably arranged in the socket, thereby completing a lock between the socket and the plug with one touch.
For example, in a tube coupling mechanism as indicated in Patent Literature 1, a sleeve is rotatably arranged in a socket. The tube coupling mechanism is provided with an operating element (front ball) and a lock element (rear ball) interposed between the socket and the sleeve, an operating element accommodating hole provided in the socket side, an operating element accommodating groove provided in a lock element accommodating hole side and in the sleeve side, an operating element accommodating groove inclined surface, a lock element accommodating groove and the like. The plug is inserted in the socket to push out the operating element and rotate the sleeve, so that the operating element is accommodated in the operating element accommodating groove. Subsequently, the lock element is pushed out to be accommodated in the lock element accommodating groove, and when the pushing-out of the lock element is eliminated, the lock element is accommodated in the plug groove to complete the lock (Patent Literature 1).